HDMI doesnt show up as playback optional

Hello,
I've been reading through all of your forum questions and have not found my problem solved yet, so I'll try asking. I've been watching movies on my laptop but playing through an HDMI cable on my tv, laptop sound worked on tv for the last month but doesn't now. I have tried going through control panel and changing speaker option to "HDMI" but the option to choose HDMI was not there. Then I right clicked my speaker in bottom right corner and clicked on "playback devices" and again the HDMI option was not there. It just has "Speakers: Realtek High Defintion Audio" and "Realtek Digital Output". Any help is greatly appreciated!
Thank you.